So the key is that on the graphic those pH values are what your all base malt mash would be, but once you add the dark malts it brings it back down to what you want it to actually be, which is 5.2-5.6. That clears it up.
In my experience depending on your water hardness, Five Star 5.2 results in a mash pH between 5.2 and 5.6 without additional salts. This is the maximum conversion efficiency range. Kaiser's pH Experiment is a good read.